1. Field of the Invention
The invention relates to a melting oven for the thermal treatment of special waste materials containing heavy metal and/or dioxin, comprising a furnace vessel which has a melting end to receive a melt, at least one charging device for the supply of the product to be treated, at least one gas outlet, at least one discharge chamber which is separated from the charging device by a separating wall and is connected in a gastight manner to the melting end by means of a siphon, at least one first heater projecting into the interior of the furnace vessel, and at least one second heater in the discharge chamber.
A melting oven of this design is known, for example, from the European Patent Application with the publication number 0 633 441 or the U.S. Pat. No. 5,574,746 of the same content.
2. Discussion of Background
During the separation of toxic, volatile chemical compounds from a mixture of solid particles, electrostatic filter dust from industrial combustion plants with pollutants which are harmful to the environment, such as for example heavy metals and their compounds, is heated in a melting furnace to over 1400.degree. C. The toxic chemical compounds and elements which evaporate during the process are removed from the melting furnace via an extractor, condensed and discharged. The non-evaporated residue is melted down successively, and the melt is discharged continuously or intermittently from the reaction space and caused to solidify. For heating, electric heaters are provided in the gas chamber of the melting furnace. These heaters are separated from the furnace atmosphere by means of ceramic protective tubes.
In this case, the discharge frequently takes place from a separate discharge chamber which is connected in a gastight manner to the actual melting furnace by means of a siphon. This prevents toxic gases from passing into the discharge chamber and thus into the environment. Since in many of the waste materials to be treated it is unavoidable that substances which are still harmful are released even in the discharge chamber, a second gas outlet with a quench arranged correspondingly downstream is required there. In addition to the cost of the quench, a considerable proportion of the heat in the discharge chamber is lost through the gas outlet.